#include<iostream>
#include<string.h>

using namespace std;

class String
{
public:
    String(const char* p = nullptr)
    {
        if (p != nullptr)
        {
            _pstr = new char[strlen(p) + 1];
            strcpy(_pstr, p);
        }
        else
        {
            _pstr = new char[1];
            *_pstr = '\0';
        }
    }
    ~String()
    {
        delete[] _pstr;
        _pstr = nullptr;
    }
    String(const String& src)
    {
        _pstr = new char[strlen(src._pstr) + 1];
        strcpy(_pstr, src._pstr);
    }
    String& operator=(const String& src)
    {
        if (this == &src)
            return *this;
        delete[] _pstr;
        _pstr = new char[strlen(src._pstr) + 1];
        strcpy(_pstr, src._pstr);
        return *this;
    }
    bool operator>(const String& src) const
    {
        return strcmp(_pstr, src._pstr) > 0;
    }
    bool operator==(const String& src) const
    {
        return strcmp(_pstr, src._pstr) == 0;
    }
    bool operator<(const String& src) const
    {
        return strcmp(_pstr, src._pstr) < 0;
    }
    int length()const
    {
        return strlen(_pstr);
    }
    char& operator[](int index) { return _pstr[index]; }
    const char& operator[](int index) const { return _pstr[index]; }
    const char* c_str() const { return _pstr; }

private:
    char* _pstr;
    friend String operator+(const String& lsrc, const String& rsrc);
    friend ostream& operator<<(ostream& out, const String& src);
    friend istream& operator>>(istream& in, String& src);
};

String operator+(const String& lsrc, const String& rsrc)
{
    char* temp = new char[strlen(lsrc._pstr) + strlen(rsrc._pstr) + 1];
    strcpy(temp, lsrc._pstr);
    strcat(temp, rsrc._pstr);
    String s(temp);
    delete[] temp;
    return s;
}
ostream& operator<<(ostream& out, const String& src)
{
    out << src._pstr;
    return out;
}
istream& operator>>(istream& in, String& src)
{
    in >> src._pstr;
    return in;
}
#if 0
int main()
{
    String str1;
    String str2 = "aaa";
    String str3 = "bbb";
    String str4 = str2 + str3;
    String str5 = str2 + "ccc";
    String str6 = "ddd" + str2;

    cout << "str6:" << str6 << endl;
    if (str5 > str6)
    {
        cout << str5 << ">" << str6 << endl;
    }
    else
    {
        cout << str5 << "<" << str6 << endl;
    }
    int len = str6.length();
    for (int i = 0; i < len; i++)
    {
        cout << str6[i] << " ";
    }
    cout << endl;

    char buf[1024] = { 0 };
    strcpy(buf, str6.c_str());
    cout << "buf:" << buf << endl;

    return 0;
}
#endif
